Dear all
I was trying to calculate the thermal conductivity of Si nanowire with Radius 75A at T=300K but I am getting very small value, 0.027[W/mK]. It should some how be around 100 [W/mK].
units real
variable T equal 300
variable V equal vol
variable dt equal 4.0
variable p equal 200 # correlation length
variable s equal 5 # sample interval
variable d equal $p*$s # dump interval
convert from LAMMPS real units to SI
variable kB equal 1.3806504e-23 # [J/K] Boltzmann
variable kCal2J equal 4186.0/6.02214e23
variable A2m equal 1.0e-10
variable fs2s equal 1.0e-15
variable convert equal {kCal2J}*{kCal2J}/{fs2s}/{A2m}
setup problem
dimension 3
boundary p p p
atom_style atomic
lattice diamond 5.43
region whole block 0 200 0 200 0 100 units box
create_box 1 whole
region wire cylinder z 100 100 75 INF INF units box
lattice hcp 5.43 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
create_atoms 1 region wire
mass 1 28.8
pair_style tersoff
pair_coeff * * …/potentials/Si.tersoff Si
timestep ${dt}
thermo $d
equilibration and thermalization
velocity all create $T 102486 mom yes rot yes dist gaussian
fix NVT all nvt temp $T $T 10 drag 0.2
dump 1 all custom 1000 Sigeometry.* id type x y z
run 10000
shell mkdir Silicon
shell cd Silicon
thermal conductivity calculation
unfix NVT
fix NVE all nve
reset_timestep 0
compute myKE all ke/atom
compute myPE all pe/atom
compute myStress all stress/atom virial
compute flux all heat/flux myKE myPE myStress
variable Jx equal c_flux[1]/vol
variable Jy equal c_flux[2]/vol
variable Jz equal c_flux[3]/vol
fix FLX all ave/correlate $s $p $d &
c_flux[1] c_flux[2] c_flux[3] type auto file Silicon.dat ave running
variable scale equal {convert}/{kB}/$T/$T/$V*s*{dt}
variable k11 equal trap(f_FLX[3]){scale}
variable k22 equal trap(f_FLX[4])*{scale}
variable k33 equal trap(f_FLX[5])${scale}
thermo_style custom step temp v_Jx v_Jy v_Jz v_k11 v_k22 v_k33
run 10000
variable k equal (v_k11+v_k22+v_k33)/3.0
print "average conductivity: $k[W/mK] @ $T K "
Thaks